Engine momentarily cuts out at 4000 rpm

Shuey

Shuey

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Joined
Jul 3, 2007
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1,532
Location
Niceville, FL
Bike
FJR1300 ES, 2018
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I've been contacted by a 2006 ST owner who is having a problem not being resolved by his local dealer in the Daytona area. He's not on the site.

He reports the bike runs fine up to 4,000 rpm, then momentarily cuts out, then kicks back in and runs fine above 4,000 rpm. It does this all the time.

I never experienced this or heard of it before. Any ideas as to the cause . . . or a fix?

Shuey
 
Re: Pblm: Engine momentarily cuts out at 4000 rpm

My guess is that it's a problem with the ECU provided that always happens at 4000 RPM. My logic is that if fuel pump and filters checked OK the problem is electrical in nature and no other part cares about numbers except the ECU for mapping purposes. A glitch in the map would make it a repeatable issue. Only way to test it swap ECU's with a bike that is not having this issue.
 
Re: Pblm: Engine momentarily cuts out at 4000 rpm

Isn't there a there is a fuel-map switch over point in the ST around ~3800 RPM? I can sometimes feel the ST stumble ever so slightly if I transition upwards slowly thru that RPM under the right ambient temperature band, coupled with a relatively no engine load riding condition.
 
Re: Pblm: Engine momentarily cuts out at 4000 rpm

Shuey said:
He reports the bike runs fine up to 4,000 rpm, then momentarily cuts out, then kicks back in and runs fine above 4,000 rpm. It does this all the time.

Shuey
Click to expand...

I had that problem with a car I owned and it turned out to be a bad spark plug cap. Finally put it on an ignition scope and could see the cylinder missing intermittently. The reason its RPM dependent is spark energy requirement varies depending on engine load and cylinder pressure, so its good most of the time, but will fail in a specific range.
 
Re: Pblm: Engine momentarily cuts out at 4000 rpm

okmurdog said:
Isn't there a there is a fuel-map switch over point in the ST around ~3800 RPM? I can sometimes feel the ST stumble ever so slightly if I transition upwards slowly thru that RPM under the right ambient temperature band, coupled with a relatively no engine load riding condition.
Click to expand...

Depending on whose dyno chart you're looking at, there's a little dip in the torque curve right around there.

--Mark
 
Great responses, thanks all. Appreciate getting some questions to ask, which I'll pass on shortly. This just isn't anything I experienced on my 3 STs, nor heard about from any of all ya'll in the past 7 years!

As to the last comment about him joining up . . . that was my first suggestion.

I'll post more when I get more.

Shuey
 
That sounds bad, seems like what's being described, except . . . you're not getting through it to a higher rpm. Does it act the same while in gear also?

Thanks for the effort and response.

I've left messages with the additional questions, but no response yet. I'll try to call again later tonight.

Shuey
 
that video looks very similar to what I experienced with my car misfire I mentioned in the previous post. Ran fine over 90% of the RPM band, but in a narrow range it misfired just like that bike is doing. That looks ignition related to me, but I don't have a lot of experience with badly running engines to say for sure.
 
There's got to be something significant with the FI lamp flashing on and off at ~4k RPM. I'd need to look at the SM for the possible fault that would give that indication, but I had the impression that the FI light stayed illuminated (solid ON) once it lit up as long as the engine is running, side stand up?
 
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